On Wed, Dec 21, 2005 at 09:58:34AM -0500, Graham Davies wrote: > In a post on November 12, I described an experiment in which an > ATmega16-16PC ran with a 15.36 MHz crystal with a wide variety of > fuse setting, including CKOPT not programmed. The experiment > included long traces and lots of stray capacitance at the crystal > pins and I later extended it to include a large imbalance in the > load capacitors. It always worked. So, it seems to me that the > crystal circuit is not really so sensitive. I withhold an opinion > about those plug-in breadboards, though. I would not use one > myself.
No offense, but your experiment is just one data point. Contrary to your experiment, I've had problems with the oscillator starting when CKOPT is unprogrammed using a 16 MHz crystal. Simply program CKOPT and it works fine, so I guess my experience contradicts yours - I used an ATmega128, perhaps it is more sensitive to this than the ATmega16, maybe it was just that particular batch of chips, I don't know. Anyway, the datasheet also says CKOPT should be programmed for these higher speed settings. So when people have trouble with the oscillator when using a 16 MHz crystal or resonator, and they are not following the recommendations of the datasheet, the first thing they should do is get in-line with the datasheet recommendations and verify that CKOPT is programmed. This is just standard checklist stuff when troubleshooting. -Brian -- Brian Dean ATmega128 based MAVRIC controllers http://www.bdmicro.com/ _______________________________________________ AVR-chat mailing list [email protected] http://lists.nongnu.org/mailman/listinfo/avr-chat
